The MCGG52H1CB0753C of GEC ALSTHOM is a high-performance microcomputerized overcurrent and ground fault relay, belonging to the classic MCGG series (usually included in the Midos system).

This series is widely used in industrial power distribution and power system protection, and is renowned for its reliable time-limited (DT) and inverse-time (IDMT) protection characteristics.

Basic parameters and model specifications: Full model name

Product type MCGG52H1CB0753C: Two-phase Overcurrent + Earth Fault Protection Relay (2 Phase Overcurrent + Earth Fault)

Rated current ($I_n$) :

1A (Commonly used in the secondary circuit after the distribution ratio

Auxiliary power supply: 48V – 125V DC (suitable for typical substation DC operating systems)

Frequency: 50/60Hz. Universal measurement features: includes Instantaneous and Time Delayed protection elements

2. Main functional features

MCGG52H1CB0753C

Protection configuration: The MCGG52 model is specifically designed for two-phase overcurrent protection along with an independent ground fault channel.

Multiple time curves: Supports multiple standard inverse-time characteristics (selected by dip switches) :

Standard Inverse (SI)

Very Inverse (VI

Extremely Inverse time limit (EI

Long Time Inverse (LTI)

And three Definite Time ranges.

Adjustment range

Current setting value ($I_s$) :

It is usually between $0.05 \times I_n$and $2.4 \times I_n$, with step-by-step refinement. Time multiplier ($TMS$) : Adjustable from 0.05 to 1.0. with a step of 0.025.

Instantaneous element (Iinst) : It can be set from $1 \times I_s$to $31 \times I_s$, and is used for rapid tripping in severe short-circuit faults

3. Physical Specifications and Installation

Case Size: Midos specification cases (Size 6 or Size 8) are usually adopted, which is convenient for insertion into standard bases.

Indicator light (LED) : The panel is equipped with an independent LED indicator light, which is used to indicate the “start” or “trip” status of two-phase and ground faults.

Maintainability: Supports online testing mode, allowing the health status of the relay to be tested through the panel buttons without disconnecting the circuit.

MCGG52H1CB0753C

4. Common Applications

Distribution line protection: Applicable to overload and short-circuit protection of medium and low voltage overhead lines or cable feeders.

Transformer backup protection: As a backup overcurrent protection for the high-voltage or low-voltage side of power transformers.

Motor protection: Provides reliable protection against locked rotor and ground faults of large motors

Technical indicators of parameter items

The number of protected phases is 2 for overcurrent and 1 for grounding

Secondary rated current: 1A

The auxiliary DC voltage is 48/125V DC

The instantaneous breaking factor is set at 1 to 31 times the current

Industrial-grade protection that complies with IEC standards